Issue failed to mount the database , Database can't be mounted on server.
Failed to determine the mount status of the active database copy. Verify that the underlying cause of the error has been corrected before attempting to mount the database. The error can be ignored and the mount allowed if Mount-Database is issued with the -Force switch
On the problem server open services.msc console
Find cluster services and re-start
You could also use PS, to find out the service name
Once you figure out the service name
Try to mount the DB after successful re-start of the cluster service